The object of the invention is a container-forming apparatus, which is of the type presented in the preamble of patent claim 1.
The invention particularly relates to the kind of container-forming apparatuses which produce horizontally circular cylindrical containers, in which at least one of the end members closing the container is sealed into the open end of the cylindrical casing by pressing the edges of the portions together. In practice, this is done in such a way that the end member, the outer edges of which are turned in the axial direction of the casing, is positioned inside the casing, after which the edge portion of the casing is folded double so that it is wrapped over the outwardly turned edge of the end member, after which pressure is applied in order to create the final seal. Prior to these mechanical stages the end member and the upper end of the casing are heated by air blowing, so that the heat-sealable substances on the surface of the above-mentioned portions are brought to a suitable condition.
These known container-forming stages are described, for example, in European patents 0 038 488 and 0 456 011.
The clamping means used in presently known container-forming units usually have a heavy and complex structure and, in addition, they cannot obtain sufficient clamping efficiency, which has a decisive effect on the tightness of the seal. The object of the invention is to introduce an improvement to the above-mentioned prior art and to present a container-forming apparatus, in which the clamping means is structurally easy to realise, and the said clamping means gives a good clamping effect that can advantageously be applied to the entire perimeter of the bottom portion of the casing and the end member. In order to implement this the container-forming apparatus according to the invention is mainly characterised by what is presented in the characterising part of the attached patent claim 1. The clamping means comprises a piston with a V-shaped front portion, which pushes the clamping members radially outwards, said clamping members being pivotally mounted to turn towards the frame, whereby the folded bottom portion of the casing wrapped around the edge of the end member is pressed between the outer surfaces of the clamping members and the clamping countersurfaces positioned outermost on the frame of the clamping means. As the clamping members are mounted on bearings to turn towards the frame, said clamping members form levers, by means of which a good force effect is obtained.
Other preferred embodiments are referred to in the attached dependent patent claims and the subsequent description.